Title of Invention

A DEVICE FOR THE PREMIXING OF ADDITIVES AND FOR FEEDING THEM INTO A POLYMER MELT STREAM

Abstract

Tne present mvennon relates to a aevIce lor me premIXIng 01 aaaIUves ana lor feeding them into a polymer melt stream. The apparatus has a conducting element 2 fIrst and a second intermediate element 4a and 4b and a pump assembly 6, wherein the polymer melt stream is guided through channels 8 and 10 of the conducting element. The second intermediate element 4a has a feed element 12 that extends into the first channel 8 to form a ring channel. The feed element 12 is surrounded by openings 14 through which a portion of the polymer melt is drawn off, so that it can be mixed with an additive in~ide the pump assembly 6. This mixture is then returned via the feed element 12 to the polymer melt stream. The apparatus according to the invention makes it possible to decrease the residence times of the polymer and requires very little in the way of apparatus.

Full Text

Device for the premixing of additives and for feeding them in a polymer melt stream The present invention relates to a device for the premixing of additives and for feeding them into a polymer melt stream. The feeding of additives into a polymer melt stream is known, Chemiefasern/Textiliindustrie, 36th/88th annual, January 1986, pages 24 to 29, describes a method for the feeding of additives into a polymer melt stream, in which a part stream is extracted from an unmodified main melt stream emerging from an end reactor or extruder and is led via a twin-shaft extruder equipped with special kneading elements. By means of a continuous metering system, the additives are supplied to the twin-shaft extruder and are worked into the polymer melt. Thereafter, the part stream laden with additives is intermixed with the main melt stream again, unifoim intermixing being achieved by means of static mixing elements. DE 40 39 857 Al discloses a device for the direct continuous modification of polymer melts, in which, again, a part melt stream is extracted from a main melt stream and is led into an extruder. The additives to be supplied pass via a feed pump into the extruder, and, thereafter, the part melt stream modified in this way is supplied to the main melt stream again. DE 198 41 37 6 Al discloses a method for the feeding of additives into a polymer melt stream, in which a part stream is branched off from the polymer melt stream and is divided into further part streams. The last-mentioned part streams are led into a planetary pump, to which at least one additive is supplied. Thereafter, the part streams are combined again and are led through a static mixer. Subsequently, the part stream is supplied to the main melt stream again. In the known devices and methods, there is the disadvantage that, at the locations of the main melt stream at which part of the polymer melt is extracted or the polymer melt enriched with additives is returned to the main melt stream again, regions arise in which sometimes undesirably long retention times or even deposits of the polymer melt occur. Furthermore, the devices entail a high outlay in terms of apparatus. The object on which the invention is based is, therefore, to provide a device for the premixing of an additive and for feeding it into a polymer melt stream, said device allowing short retention times of the polymer and entailing a low outlay in terms of apparatus, This object is achieved by means of the features specified in patent claim 1. Advantageous embodiments of the invention are the subject matter of the subclaims. The device according to the invention for the premixing of additives and for feeding them into a polymer melt stream has a line element with a first duct and with a second duct issuing laterally into the first duct. The line element is inserted into a line, in which the polymer melt stream is guided, so that the polymer melt flows through the second and the first duct, Furthermore, a planetary pump with at least n = 3 planet wheels is provided, to which inflow and outflow ducts lead, each planet wheel of the planetary pump being assigned an inflow duct and an outflow duct. At least one and at most n-1 inflow ducts are designed as additive inflow ducts, and the remaining inflow ducts are designed as polymer melt inflow ducts. By an additive inflow duct is to be meant a duct via which an additive can be introduced into the planetary pump from a corresponding device, while the polymer melt inflow ducts extend with one mouth up to the polymer melt stream and with the other mouth into the planetary pump. Furthermore, according to the invention, a feeding element is provided, which is flow-connected to the outflow ducts and which extends into the first duct so as to form an annular duct. Those mouths of the polymer melt inflow ducts which face away from the planetary pump are arranged around the feeding element. The feeding element may be a tube-like end piece, such as, for example, a nozzle. The annular duct is then the space surrounding the feeding element, between the outer wall of the feeding element and the wall of the first duct. The latter does not necessarily have to be annular. During operation, part of the polymer melt is sucked out of the polymer melt stream through the mouths of the polymer melt inflow ducts in the direction of the planetary pump. Since the mouths of the polymer melt inflow ducts are distributed around the feeding element, the polymer melt is sucked uniformly out of the annular duct. This positive guidance makes it possible to ensure that there are no regions in which the polymer melt is retained for a relatively long time or is even deposited on account of a lower velocity. Moreover, the outlay of the device according to the invention in terms of apparatus is lower, since the extraction of a part of the polymer melt and the return of the polymer melt enriched with the additive take place at the same location, that is to say in the same tubular connection piece. Thus, only the line element of the device according to the invention is necessary in the main line for the polymer melt stream, and the two connection pieces for extraction and return, required in the known devices, may be dispensed with. The mouths of the polymer melt inflow ducts are arranged preferably symmetrically around the feeding element, so that the polymer melt can be sucked out of the polymer melt stream uniformly. A symmetric arrangement may be based both on point symmetry and on axial symmetry. Thus, for example, the mouths may be arranged circularly or ovally around the feeding element. Since the polymer melt stream flows first through the second duct and then through the first duct, the greatest risk that the polymer will be deposited is in that region of the annular duct which faces away from the second duct. Consequently, in the preferred embodiment of the device according to the invention, a mouth of a polymer melt inflow duct is arranged in this region. In an advantageous embodiment of the device according to the invention, the feeding element is designed conically in a region facing • away from the outflow ducts. A largely uniform flow of the polymer melt stream in the annular duct is thereby achieved. Preferably, in a further embodiment of the device according to the invention, the second duct is arranged at right angles to the first duct. Since, in the case of a relatively low number of additive inflow ducts, some outflow ducts carry only the pure polymer melt, at least one static mixer is arranged between the outflow ducts and the feeding element, in order to ensure a greater intermixing of the additive-laden polymer melt with the pure polymer melt. Even when all the outflow lines already carry an additive/polymer-melt mixture, the static mixer contributes to better intermixing. In a further advantageous embodiment of the device according to the invention, two static mixers arranged one behind the other in the direction of flow are provided. The outflow ducts which carry an additive/polymer-melt mixture extend into the static mixer which is first in the direction of flow, whereas the outflow ducts carrying pure polymer melt extend into the static mixer which is second in the direction of flow. An arrangement of this type leads to particularly intensive intermixing of additive and polymer melt. In order to ensure simpler maintenance, repair and handling, the planetary pump, the inflow ducts, the outflow ducts and the feeding element are advantageously connected rigidly to one another and are fastened to the line element via a common fastening means. Should static mixers be provided, these are preferably likewise connected rigidly to the abovementioned elements. The rigidly connected elements can be separated simply and quickly, together, from the line element in which the polymer melt stream flows. The fastening means preferably has a flange which can be flanged on the line element. The present invention is explained in more detail below by means of exemplary embodiments, with reference to the accompanying figures of which: fig. 1 shows a perspective partially sectional illustration of the device according to the invention in a first embodiment, fig. 2 shows a perspective partially sectional further illustration of the device of fig. 1, figs. 3 to 5 show perspective illustrations of the second intermediate element of figs. 1 and 2 in a partially sectional illustration. figs. 6 and 7 show perspective illustrations of the second intermediate element of figs. 3 and 4, fig. 8 shows a side view of the pump subassembly of figs. 1 and 2 in a sectional illustration, fig. 9 shows a top view of the sectional line A-A of fig. 7. Fig. 1 shows the device according to the invention in a first embodiment. The device has a line element 2, a first and a second intermediate element 4a, 4b and a pump subassembly 6 which are arranged one above the other in the abovementioned order. The line element 2 comprises a first duct 8, which extends axially through the entire line element 2, and a second duct 10. The second duct 10 extends from outside the line element 2 into the first duct 8, the first and the second duct 8, 10 running at right angles to one another. The first intermediate element 4a is designed essentially in the form of a circular disk and can be flanged to the line element 2 in such a way that the first duct 8 is closed at one end. The first intermediate element 4a has an essentially tubular feeding element 12 which, after the first intermediate element 4a has been flanged to the line element 2, extends into the first duct 8-Moreover, five mouths 14 are provided on the downwardly pointing side of the first intermediate element 4a. The mouths 14 belong to inflow ducts 20 (fig. 2) . The mouths 14 are arranged circularly, preferably symmetrically, around the feeding element 12. Fig. 2 shows a perspective partially sectional further illustration of the device of fig. 1. With the device in operation, the polymer melt stream, not illustrated, flows first through the second duct 10 and thereafter through the first duct 8, the direction of flow being indicated by the arrows a. The feeding element 12 has a first portion 12', which is of essentially cylindrical design, and a second portion 12', which faces away from the first intermediate element 4a and which converges conically in the direction of flow. In a similar way to this, the first duct has a first cylindrical portion 8' and a conical second portion 8'. Between the wall of the first duct 8 and the outer wall of the feeding element 12 is formed an annular duct 16 which has an essentially constant flow cross section over the entire length. The second portion 8' ' of the first duct 8 has adjoining it in the direction of flow a third portion 8'', the flow cross section of which corresponds, in turn, to the flow cross section of the second duct 10. Within the feeding element 12, a first feeding duct 18a extends in the axial direction as far as that side of the first intermediate element 4a on which the second intermediate element 4b is mounted, a first static mixer 19a being arranged in that region of the first feeding duct 18a which faces the second intermediate element 4b. A second feeding duct 18b extends in the axial direction in the second intermediate element 4b and is, arranged in alignment with the first feeding duct 18a. Within the second feeding duct 18b is arranged a further static mixer 19b. The static mixers 19a, 19b are indicated merely diagrammatically and may consist, for example, of a plurality of guide elements arranged in an offset manner. Figs. 3 to 5 or 6 and 7 show the second intermediate element of fig. 1 in a partially sectional or nonsectional perspective illustration respectively. Five polymer melt inflow ducts 20 extend, parallel to the second feeding duct 18b, through the second intermediate element 4b. These polymer melt inflow ducts 20 extend, moreover, through the first intermediate element 4a, and their mouths 14 can be seen in figs. 1 and 2. Furthermore, an additive inflow duct 22 is provided, which extends (fig. 7) outward as far as a side of the second intermediate element 4b on which the additive can be supplied via a line 24 or the like. The additive inflow duct 22 is arranged within the second intermediate element 4b, in order to avoid long line paths, the additive addition being identified by the arrow b (fig. 7). Fig. 8 shows a side view of the pump subasserribly 6 in a sectional illustration. The pump subassembly 6 has a planetary pump with a lower plate 30, a middle plate 32 and an upper plate 34, six planet wheels 36 (only one is illustrated) and a spur gearwheel 38 being arranged within clearances in the middle plate 32. The planet wheels 36 are arranged in each case on a rotatable shaft 40 and the spur gearwheel 38 is arranged on a drive shaft 41. The drive shaft 41 extends through the upper plate 34 and a fastening plate 44 adjacent to the latter. The fastening plate 44 serves for fastening a drive unit, not illustrated, for driving the drive shaft 41. It is evident from fig. 8, and also from fig. 9 which shows a top view of the sectional line A-A of fig. 8,. that the polymer melt inflow ducts 2 0 and the additive inflow duct 22 extend through the lower plate 3 0 of the planetary pump vertically upward into the region of the planet wheels 36 and end there. According to the principle of a planetary pump, the stream from an inflow duct 20 or 22 is divided into two identical parts in the toothed spaces of a sunwheel and planet wheel. Accordingly, an outflow duct is assigned the two halves of two adjacent inflow streams from the inflow ducts. The inlet mouth of an outflow duct 42 is arranged in each case in the immediate vicinity of each planet wheel 36. The outflow ducts 42 extend through the lower plate 30 of the planetary pump. Those outflow ducts 42 which contain, inter alia, the additive run in this case obliquely inward, so that they end in a common region 44. Those outflow ducts 42 which carry only polymer melts run vertically through the lower plate 30. With the device assembled, the region 44 and the upwardly pointing end of the second feeding duct L8b lie congruently one above the other. rhe functioning of the device in the first embodiment is described below. The polymer melt stream flows in the direction of the arrows a (fig. 2) through the second and the first duct 10, 8 - The drive unit (not illustrated) operates the planetary ptimp (fig. 8) via the drive shaft 41, with the result that part of the polymer melt stream is sucked through the mouths 14 (fig. 1) into the polymer melt inflow ducts 20 (fig. 2) . In parallel with this, an additive is forced out of the line 24 into the additive inflow duct 22. The polymer melt or the additive passes via the inflow ducts 20, 22 into the planetary pump (figs. 7 and 8) . Within the planetary pump, with the gearwheels conveying the additive, additive and polymer melt are combined. Thereafter, an additive/polymer-melt mixture flows through the two outflow ducts 42 directly adjacent to the additive inflow duct 22, whereas pure polymer melt flows back through the other putflow ducts 42 (fig. 8) . The additive/polymer-melt mixture passes, via the outflow ducts 42 which carry the additive/polymer-melt mixture, into the second static mixer 19b within the second feeding duct 18b (fig. 2) , in order to be intermixed intensively there. Subsequently, the mixture thus obtained emerges from the second feeding duct 18b and passes into the first feeding duct 18a, where it is intermingled with the polymer melt from the other outflow ducts 42 (fig. 5) . Instead of only one additive inflow duct 22 being provided, one or more polymer melt inflow ducts 20 may also be utilized for the supply of additive into the planetary pump. In this case, the inflow ducts are combined in the second intermediate element 4b via an annular duct and are acted upon by additive via a common inflow bore. Patent claims 1. A device for the premixing of additives and for feeding them into a polymer melt stream, having a line element (2), in which the polymer melt stream is guided, a planetary pump with at least n = 3 planet wheels (36) , in each case an inflow duct (20, 22) and an outflow duct (42) for each planet wheel (36), at least one and at most n-1 inflow ducts being designed as additive inflow ducts (22) , and the remaining inflow ducts being designed as polymer melt inflow ducts (20), and a feeding element (12) which is flow-connected to the outflow ducts (42) , characterized in that the line element has a first duct (8) and a second duct (10) issuing laterally into the first duct (8) , the feeding element (12) extending into the first duct (8) so as to foirm an annular duct (16), and those mouths (14) of the polymer melt inflow ducts (20) which face away from the planetaory pump being arranged around the feeding element (12). 2. The device as claimed in claim 1, characterized in that those mouths (14) of the polymer melt inflow ducts (20) which face away from the planetary pump are arranged symmetrically around the feeding element (12). 3. The device as claimed in one of claims 1 or 2, characterized in that one mouth (14) of a polymer melt inflow duct (20) which faces away from the planetary pump is arranged in a region of the feeding element (12) which faces away from the second duct (10). 4. The device as claimed in one of the preceding claims, characterized in that the feeding element (12) is designed conically in a region facing away from the outflow ducts (42) . 5. The device as claimed in one of the preceding claims, characterized in that the second duct (10) is arranged at right angles to the first duct (8) . 6. The device as claimed in one of the preceding claims, characterized in that at least one static mixer (19a, 19b) is arranged between the outflow ducts (42) and the feeding element (12). 7. The device as claimed in claim 6, characterized in that two static mixers (19a, 19b) arranged one behind the other in the direction of flow are provided, the outflow ducts (42) which carry an additive/polymer-melt mixture extending into the static mixer (19b) which is first in the direction of flow, and the outflow ducts (42) which carry the polymer melt extending into the static mixer (19a) which is second in the direction of flow. 8. The device as claimed in one of claims 1 to 5, characterized in that the planetary pump, the inflow ducts (20, 22) , the outflow ducts (42) and the feeding element (12) are connected rigidly to one another and are fastened to the line element via a common fastening means. 9- The device as claimed in one of claims 6 or 7, characterized in that the planetary pump, the inflow ducts (20, 22), the outflow ducts (42), the feeding element (12) and the static mixers (19, 42) are connected rigidly to one another and are fastened to the line element via a common fastening means. 10. The device as claimed in one of claims 8 or 9, characterized in that the fastening means has a flange. 11. A device for the premixing of additives and for feeding them into a polymer melt stream substantially as herein described with reference to the accompanying drawings.

Documents:

466-chenp-2003-abstract.pdf

466-chenp-2003-claims duplicate.pdf

466-chenp-2003-claims original.pdf

466-chenp-2003-correspondnece-others.pdf

466-chenp-2003-correspondnece-po.pdf

466-chenp-2003-description(complete) duplicate.pdf

466-chenp-2003-description(complete) original.pdf

466-chenp-2003-drawings.pdf

466-chenp-2003-form 1.pdf

466-chenp-2003-form 26.pdf

466-chenp-2003-form 3.pdf

466-chenp-2003-form 5.pdf

466-chenp-2003-other documents.pdf